Variable generation sources such as wind, solar photovoltaic, hydro or other variable sources, while capable of generating sometimes significant energy, do not generate reliable enough output to be able to be counted upon for critical or even typical loads. One example of a critical load may be that refrigeration within a pharmacy or doctor's office needs constant power to assure proper operation. The intermittent nature and variability of these types of generation is only randomly in synch with the load on site, as the generation is generally not controllable.
In typical commercial and many smaller configurations, electric utilities charge different rates for energy and power, and the rates are often differently based on time of day and day of week. The previously described variable characteristics in a traditional variable generator system result in variable generation affecting the energy portion of the utility bill but NOT affecting the power (aka demand) portion of the bill. As the demand portion can be as much as 40% of a typical commercial bill, an improvement over traditional system could make a significant impact on the financial return (savings or impact on demand portion of bill) when utilized together with the variable generator.
Thus, a need exists for more intelligent power charge and discharge systems and methods, which effectively utilizes an energy storage system in conjunction with a variable generator.